Perspiration-inhibiting compositions in the form of a water-in-oil emulsion are already known in the existing art. WO 92/05767 A1 discloses transparent perspiration-inhibiting gels in the form of a water-in-oil emulsion based on cyclomethicones and emulsifying ethylene oxide/propylene oxide-substituted polydimethylsiloxanes. WO 96/06594 A1 discloses transparent perspiration-inhibiting water-in-oil compositions that contain volatile silicone oils and/or volatile hydrocarbon oils, and the silicone-free water-in-oil emulsifiers Laureth-1 or Laureth-4. WO 98/17238 A1 discloses perspiration-inhibiting sticks in the form of a water-in-oil emulsion based on silicone-free water-in-oil emulsifiers terminally disubstituted with alkyl residues, without addressing the problem of transparency. WO 00/67888 A1 discloses low-viscosity W/O emulsions having a viscosity of at most 5000 mPas, at least 75 wt % water phase, at most 20 wt % lipids, emulsifiers, and further lipophilic constituents, the oil phase having a total polarity between 20 and 30 mN/m and being free of silicones, stabilized by means of silicone-free water-in-oil emulsifiers terminally disubstituted with alkyl residues. This document also does not deal with the problem of transparency.
Transparent gels in the form of a water-in-oil emulsion are very popular among consumers. The known propellant gas-free W/O gels based on cyclomethicones produce a fresh and at the same time care-providing feel when applied onto the skin. At the same time, they initially exhibit no residues directly after application. This (at first) largely residue-free application, which is greatly appreciated by consumers, is also made visible to them by the transparency of the composition.
For optimum transparency, the refractive index of the oil phase and of the water phase must be matched to one another within approximately 0.001 or better, and preferably within approximately 0.0004. If a constituent resulting in a relatively high refractive index for the aqueous phase is stipulated, for example the particularly effective perspiration-inhibiting aluminum-zirconium compounds, this therefore limits the selection of the other constituents.
One problem with the known gels is their high cyclomethicone content. In the context of commercially usual cyclomethicones, a distinction is made principally among cyclotetrasiloxane, cyclopentasiloxane, and cyclohexasiloxane. Cyclotetrasiloxane, whose melting point of −11° C. is unusually high, can result in problems with shelf stability at the higher utilization quantities that are typical for a water-in-oil emulsion gel. In addition, the use of cyclotetrasiloxane is largely falling out of favor nowadays for toxicological reasons. The usual commercial cyclomethicone products are largely free of cyclotetrasiloxane. Even the trace concentration of cyclotetrasiloxane, however, means that the cyclomethicone substance class is a problematic raw material; cyclosiloxanes in general are furthermore being discussed because of their persistence in the environment. On the other hand, the cyclomethicones exhibit outstanding utilization properties, so that it is extremely difficult to replace them. Cyclomethicones are relatively volatile oil components. They are therefore popular for use in cosmetics, in particular in antiperspirants, because they help solve the problem of clothing stains. On the other hand, antiperspirants having too high a proportion of volatile cyclomethicones form white residues on the skin after drying, i.e. not until some time after application, which adhere poorly to the skin and can flake off; this is perceived by many consumers as unpleasant.
It would therefore be desirable to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that are largely or in fact entirely free of cyclomethicones. It would be further desirable to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that have a high concentration of dispersed aqueous phase, by preference at least 75 wt %. Because the commercially usual perspiration-inhibiting active substances are water-soluble, they are present in the aqueous phase. Rapid release of the active substance can be assisted by a high concentration of aqueous phase, and can be greatly improved by selecting the emulsifiers and additives in the aqueous phase.
Another desirable goal would be to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that have a gel-like consistency of medium to high viscosity, and can be applied by means of a roll-on applicator or a stick-like sleeve (cream dispenser). It would also be advantageous to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that are largely or in fact entirely free of cyclomethicones and exhibit good release of the perspiration-inhibiting active substance.
It would also be advantageous to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that are largely or in fact entirely free of cyclomethicones and have sufficient shelf stability. Another desirable goal would be to make available transparent perspiration-inhibiting compositions in the form of a water-in-oil emulsion that are largely or in fact entirely free of cyclomethicones and have sufficient shelf stability, and exhibit good release of the perspiration-inhibiting active substance.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.